What is a hybrid car?

Hybrid cars combine a battery and engine for fuel efficiency and long range. Here's the full guide

BuyaCar team
Mar 15, 2019

Cars like the Toyota Prius (above) and Hyundai Ioniq are both examples of hybrids. These types of car use two different types of power, usually a combination of a battery and electric motor with either a petrol or diesel engine.

These elements provide the low emissions and smooth performance of an electric car, with the long distance between fill ups associated with petrol or diesel cars. The real-world fuel economy of the newest Toyota Prius is a whopping 70mpg, around 20mpg better than a similarly sized diesel car.

There are also plug-in hybrids, which offer up even more economy, as they have bigger batteries that can be charged up from a socket. These can travel on pure electric, albeit for only around 15-30 miles.

As well as good fuel economy, hybrid cars also have low carbon dioxide emissions, which helps to reduce their company car tax bill - by thousands of pounds for some plug-in hybrid models.

But in the real-world, fuel consumption and emissions vary considerably depending on how you drive the cars. Hybrids also tend to be more expensive than non-hybrid cars, and can feel heavy in corners because of the extra weight of the battery

Some sportscar manufacturers use hybrid technology for lightning performance. Because electric motors provide an instant burst of power as soon as you press the accelerator (unlike an engine that needs revving), they have been used by the likes of McLaren, Ferrari and Porsche to bring explosive acceleration to their hypercars.

Even in mainstream models, the electric part of hybrid systems makes cars feel nippy as they move away from a standstill.

Pros and cons of hybrid cars

Pros of hybrid cars

✔  Excellent fuel economy - especially in town
✔  Generally reliable
✔  Low emissions cut company car tax
✔  Low emissions cut road tax too
✔  Congestion charge exempt
✔  Quiet when using just electric power
✔  Can improve acceleration with an instant burst of power

Cons of hybrid cars

Usually more expensive than a petrol or diesel car
Less effective on long-distance journeys
Heavy batteries can make hybrids less responsive in corners
Plugging in a plug-in can be a pain
Tends to be reserved for sensible cars
Gimmicky and complex entertainment menus
Big hybrid badging can be seen as gaudy

How do hybrid cars work?

A conventional hybrid car is able to use energy that’s usually lost when the car is braking to recharge its battery (at the back in the Toyota Prius diagram below).

It’s effectively ‘free’ energy that can be used to power an electric motor, which is used to drive the car, reducing the amount of fuel required.

Most hybrids can drive at low speeds for a short distance using motor power alone. When more speed is needed, or the battery runs low, the petrol or diesel engine is automatically started up.

But the hybrid system is at its most useful when you’re accelerating. This is when a petrol or diesel car usually uses most fuel because you’re revving the engine harder. Hybrid cars don’t need to be revved as hard because the electric motor can operate at the same time as the engine, boosting power without using much more fuel.

The engine is usually used to keep the car at a steady speed, when it runs most efficiently. It may also charge the battery at the same time. The car's software will work out when this can be done without using much - or any - extra fuel.


What is a plug-in hybrid car?

Plug-in hybrid cars have bigger batteries that can supply enough energy to power a car on electric power alone for short journeys typically up to 15 miles - and at motorway speeds. The engine may never turn on for short commutes or school runs.

As with a standard hybrid, the motor can also be used at the same time as the engine to boost power and provide fast acceleration without revving the engine hard. The larger batteries enable the motor to do this more frequently and for longer than standard hybrid cars.

The large batteries cannot be charged through braking alone, so - as their name suggests - the cars can be plugged in and charged up.

What is a self-charging hybrid?

The term self-charging hybrid has been dreamt up by Lexus' advertising department to describe its hybrid cars. But in actual fact, all non-plug-in hybrids are self-charging because they regenerate their electrical power through things like regenerative braking. Therefore, they always have a supply of energy. The term self-charging is also a clever dig from Lexus at pure electric cars, because their electrical power has to be replenished by the driver.

See the best hybrid SUVs


What hybrids are there?

As well as the familiar Toyota Prius, there’s also a wide range of other hybrid family cars. These include the Hyundai Ioniq (above), Kia Niro and Toyota Auris.

The BMW 330e, Mercedes C350e, Audi A3 Sportback e-tron and Volkswagen Passat GTE are all plug-in hybrid versions of family cars.

There’s an increasing range of tall and rugged crossovers and sport utility vehicles (SUVs) with hybrid versions available too. These include the Toyota C-HR Hybrid, Mini Countryman S E All4, Mitsubishi Outlander PHEV, Audi Q7 e-tron, Volvo XC90 T8 and Range Rover HEV.

The BMW i8 (below) uses plug-in hybrid power to boost performance, as did the limited edition McLaren P1 and Porsche 918 Spyder.

More and more cars are using mini hybrid systems to save fuel - such as the Mazda 6 and Smart ForTwo. These systems can only store a small amount of energy and aren't branded as hybrids.


Is it worth buying a hybrid?

The more frustrating your drives are, the more likely a hybrid is likely to save you money. Hybrids are at home amongst congestion and traffic lights because you’re braking frequently, allowing the batteries to recharge, and accelerating regularly - which is when the electric motor is most effective. It’s no accident that urban taxi drivers favour the Toyota Prius.

Most hybrids also have petrol engines, which should mean that they avoid any future diesel taxes that are introduced in an attempt to improve air quality.

Hybrid cars have low carbon dioxide emission ratings but they can’t match those of plug-in hybrids. Because of the way that official tests are conducted, plug-in hybrid cars are ranked as extremely efficient, which often places them in the very lowest company car tax band - offering considerable savings for business users.

They can be frugal on fuel in the real world too. If you usually drive less than 15 miles a day - and can charge up your car at either end - then your plug-in hybrid is likely to use little or no fuel.

But the longer your drive, the closer your fuel economy will be to a non-hybrid car. In many cases, it can be worse, particularly with large petrol SUVs such as the Volvo XC90 T8 (above). Its engine is less efficient, when the battery is out of power, than the diesel option.


What are the downsides of a hybrid?

Hybrid cars - particuarly plug-in versions - are usually more expensive than non-hybrids. Fuel savings and lower taxes can more than repay the difference, but only if you’re driving far enough in the right conditions.

Weight is also an issue. The batteries and motor used in hybrids add noticeably to the weight, especially for plug-in cars with much bigger batteries. It can mean that they are less efficient than non-hybrids on longer journeys at steady speeds, because they are dragging more weight around but not benefitting from hybrid efficiency because there’s little braking involved.

Although there is more to go wrong - and questions about the reliability of hybrid batteries, which are recharging and discharging several times per journey - hybrids are seen as fairly reliable.

The most popular hybrid, the Toyota Prius was ranked the 16th most reliable car out of 150 in the latest Auto Express Driver Power customer satisfaction survey. It comes with a five-year warranty, limited to the first 100,000 miles, which is longer than average.


Hybrid power modes

You'll usually be offered the choice of driving modes in a hybrid car, which help you to boost efficiency or power. The default is usually known as 'hybrid mode'. On many hybrids there's no button for this: it's the default mode that that car is on when it starts up.

EV (electric vehicle) or Pure mode will force the car to drive on electric power alone. You might want to drive quietly and without emissions in town - or perhaps you want to drive away early in the morning without waking your neighbours up. This mode is most useful in plug-in hybrid cars, as it can be used for several miles and at high speeds. In a standard hybrid, which can't be plugged in, the car's engine will start automatically if the battery runs low - which doesn't take long - or you drive much faster than 30mph. In some cases, the limit is even lower.

Power mode focuses less on efficiency and more on providing maximum performance when you press the accelerator. The engine and electric motor work together to give the car as much power as possible, and the engine will rarely turn off.

Some hybrids, including Toyotas, have an Eco mode, which restricts performance to boost fuel economy. The car will be slow to accelerate, as the engine is kept at low revs to be as efficient as possible.


Hybrid power mode buttons


How are hybrid cars affected by the new car tax rules?

All hybrids sold after April 1 will pay the same rate of tax as every other car, except electric models. Along with other efficient models, hybrid cars will suffer from some of the most severe car tax increases.

What is a mild hybrid?

Unlike other hybrids, mild hybrids don’t use their electric power as a direct means of propulsion. Systems in the Suzuki Swift SHVS and the Suzuki Ignis SHVS use the mild hybrid system to help power electrical items in the car like the radio and sat nav, as well as to help out the start-stop system. Less mild, mild hybrid systems, like in the Audi A8 MHEV, can help turn the car off while it’s coasting, to improve MPG.


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